The present invention relates to a method for the catalytic epoxidation of olefines with hydrogen peroxide in the presence of a transition metal porphyrin complex in which a required charge equalization is performed by an anion.
Olefine oxides (oxiranes) are compounds which have significant importance in industry. They are used in the manufacture of lacquers, for preparing polyethers, polyurethanes, epoxide resins, detergents, glycols and a plurality of organic intermediate products (cf. U.S. Pat. No. 2,412,136 and DE-AS 11 39 477).
Various methods are already known in the art for the epoxidation of olefines. For example, oxiranes can be prepared according to the chlorohydrin method by reacting olefines with chlorine or sodium hypochlorite in alkaline medium and subsequently treating with bases. A primary disadvantage of this method is the formation of saline, environmentally damaging, waste water and of undesirable, chlorinated byproducts (cf. Ullmann's Enzyclopaedie der technischen Chemie (Ullmann's Encyclopedia of Technical Chemistry] vol. 10, p. 565 (3d. edition)).
A further known process is based on the reaction of olefines with organic hydroperoxides in the presence of a catalyst (cf. DE-AS 14 68 012). This second route of synthesis has the decisive disadvantage that due to the stoichiometry of the epoxidation reaction, the customarily expensive organic hydroperoxide (ROOH, wherein R is e.g. a lower-molecular group such as t-butyl or cumyl) is converted into large amounts of the corresponding alcohol (ROH) during the reaction according to the equation: ##STR1## If the corresponding alcohol can not be utilized, it must be separated from the desired product of the reaction and removed or converted via several method stages into the corresponding hydroperoxide, thereby rendering the epoxidation method economically expensive.
Another method of synthesis is based on the use of organic peracids obtained by air oxidation of the corresponding aldehydes or from carboxylic acids with hydrogen peroxide (cf. BE- 535 068). The use of these organic percarboxylic acids is always associated with a risk due to their decomposability and therefore requires expensive precautionary measures as regards the performance of the method and the design of the equipment. In addition, large amounts of the corresponding carboxylic acids are always produced in epoxidations with organic peracids which carboxylic acids must be separated and removed or returned in a stoichiometric or excess stoichiometeric amount.
The described disadvantages can be eliminated by using hydrogen peroxide as the epoxidation agent, since according to theory only water should accumulate in addition to the epoxidation product. Since the reactivity of hydrogen peroxide is weak in relation to olefines, epoxidations are performed with this reagent in the presence of catalysts. Catalysts such as molybdenum compounds and tungsten compounds are suitable only for a few olefines. In this connection, see e.g. GB 837,464 in which the various metal catalysts described in "J.A.C.S.", vol. 59, pp. 2342 to 2344, 1937 are used, U.S. Pat. No. 2,786,854, in which tungstic acid is used, U.S. Pat. No. 2,833,787, in which acidic salts of metals of the VI group of the periodic system of the elements, e.g. of tungsten and molybdenum, are used, BE 860,776, in which tungsten-containing and molybdenum-containing compounds are used, U.S. Pat. No. 3,993,673, in which arsenic-containing catalysts are used, U.S. Pat. No. 3,953,362, in which a molybdenum-containing catalyst is used, U.S. Pat. No. 4,026,908 in which mercury derivatives plus a compound of molybdenum, tungsten, vanadium or titanium is used, U.S. Pat. No. 3,806,467, in which organic and inorganic tin compounds plus organic or inorganic compounds containing molybdenum, tungsten, vanadium, selenium or boron are used, Bull. Chem. Soc. Jap. 42, pp. 1604, 1969, in which selenium dioxide is used and U.S. Pat. No. 3,778,451, in which compounds of molybdenum, tungsten, vanadium, niboium, tantalum, uranium and rhenium are used.
These substances are catalytically active; however, for various reasons the methods which can basically be executed with them are not used in technology. In conjuction with hydrogen peroxide solutions, either the hydrogen peroxide is rapidly broken down by them or only an unsatisfactory epoxidation speed is achieved. Methods employing these catalysts are also problematic because, frequently rather large amounts of byproducts, such as diols and ketones, are formed in addition to the desired epoxidation product; the separation of which byproducts can pose considerable difficulties.
Experiments have also already been undertaken to carry out methods for the catalytic epoxidation of olefines with other epoxidation agents using metal prophyrin complexes as catalysts. Epoxidation agents used in this connection were compounds such as iodoso benzene (PhIO) (Groves, J. T.; Nemo, T. E.; Myers, R. S., J. Am. Chem. Soc., 101, p. 1032, 1979, alkali metal hypochlorite such as NaOCl or LiOCl (Guilmet, E.; Meunier, B.; Tetrahedron Lett. 1980, 4449) as well as organic hydroperoxides such as t-butyl hydroperoxide or cumol hydroperoxide (Ledon, H. J.; Durbut, P.; Varescon, F., J. Am. Chem. Soc. 103, 3601, 1981. Chloroiron (III)-tetraphenyl porphyrin (FeCl) (TPP), chloro-manganese (III)-tetraphenyl porphydrin (MnCl) (TPP) or chloro-chromium (III)-tetraphenyl porphyrin (CrCl) (TPP) have been suggested, for example, as metal catalysts suitable for reaction with these epoxidation agents. Manganese (III)-tetraphenyl porphyrin has also already been used with hydrogen peroxide as oxidation agent (Renaud, J. -P.; Battioni, P.; Bartoli, J. F.; Mansuy, D., J. Chem. Soc., Chem. Commun. 1985, 888). To be sure, these catalysts have a strong decomposing action on H.sub.2 O.sub.2, so that the selectivities which can be achieved in regard to hydrogen peroxide are only very slight unless expensively substituted porphyrin ligands are used.
Oxo porphyrin complexes such as oxochloro(5,10,15,20-tetraphenyl porphyrin)-molybdenum (V) (O=Mo(TPP)Cl) have also been suggested in conjunction with organic hydroperoxides. However, an experiment to use hydrogen peroxide instead of an organic hydroperoxide with a catalyst of the composition oxo(5,10,15,20-tetraphenyl porphyrin)-molybdenum (V) methoxide for epoxidizing the olefin cyclohexene failed: No epoxidation could be observed (F. Varescon, thesis, The University of Claude Bernard-Lyon I, 1982).